Synthesis
Preparation of 3-aminopyrazine-2-carbaldehyde: Methyl 3-aminopyrazine-2-carboxylate (11 g) was dissolved in tetrahydrofuran (THF) and the solution was cooled to -78 °C. At -78 °C, diisobutylaluminum hydride (1 M hexane solution, 250 mL) was slowly added and the reaction mixture was stirred for 4 h, keeping the reaction temperature constant. Subsequently, the reaction system was slowly warmed to 0 °C and stirring was continued for 1 hour. Upon completion of the reaction, the reaction was quenched by slow addition of 1M hydrochloric acid solution. The organic and aqueous layers were separated by adding ethyl acetate to the reaction mixture for extraction. The organic layer was dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. The concentrated residue was ground in hexane to afford the target product 3-aminopyrazine-2-carbaldehyde (3.0 g, 34% yield). The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-D6): δ 7.73 (br, 2H), 8.07 (d, J = 2.25 Hz, 1H), 8.36 (d, J = 2.11 Hz, 1H), 9.95 (s, 1H).
References
[1] Patent: WO2006/63167, 2006, A1. Location in patent: Page/Page column 70-71
[2] Journal of Molecular Structure, 2005, vol. 741, # 1-3, p. 67 - 75
[3] Patent: WO2004/16600, 2004, A1. Location in patent: Page 36; 37
[4] Patent: WO2008/71937, 2008, A1. Location in patent: Page/Page column 21
